Multiple range indicator



W.' M.A PAGE 1 v MULTIPLE RANGE INDICATOR,

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MULTIPLE RANGE INDICATOR Fild Jan. 6. 1 2 Smets-Sheet 2 www Rober@ M ff Patented Nov. 2, 1948 UNITED ,STATES PATENT oi-*l-"icla l1 Claims.

(Granted under the act or March 3, amended April 30, 1928; 370 O.

This invention relates to a radio ech'o ranging device and more particularly to a method` and means for reliably indicating ranges of objects in a manner to readily establish the truth or i'alsity of such indications.

Radio echo ranging devices operate by the propagation of a. regular series of very short pulses of radio frequency energy, reflections of which from objects within the range of the device are received and caused to produce an indication of th'e distance of the object, from the device. This is accomplished by synchronizing the transmitted pulses with a recurring time trace applied along one coordinate on the screen of a cathode ray tube in such a manner that each sweep of the time trace is initiated at the same instant th'at a pulse is transmitted. The transmitted pulse and any Vechoes of it which may be received are applied to the deflection plates of the cathode ray tube in a manner to cause movement of the cathode ray beam along another coordinate, thus producing a visible deviation of the time trace. The deviation caused by the transmission of the pulse is located at the origin of the trace and the position along the trace of each deviation due to an echo is an' indication of the distance of the reflecting object from the device.

In such devices the time between pulses is chosen to equal the time of travel of a pulse to an object at the maximum desired range and return. 'Ihis range is limited by the'curvature of the earth and the elevation of the device and by the length of time trace which is :feasible at a calibration which will give a desired degree of accuracy. Y

In most conditions of use it is possible and often likely that reiiections may be hadirom objects beyond the maximum range for Whiiih' the device is calibrated. For example distant mountain ranges or planes may cause indications. Such indications will not be truly shown oxrlthe cathode ray tube but would appear tocome"from objects lying within the calibrated range of the device. For example if the maximum range of the device be 25 ymiles a reection from an objebt 30 miles distant will appear to come from an object miles distant.

It is an object of this invention to provide a method and means for distinguishing between such" correct and erroneous indications. It is another object of this invention to provide a manually operable means for distinguishing between correct and erroneous indications of distance. It is a further object of this invention to provide an automatic and continuously operable means -ior 1883, as G. 757) distinguishing between correct and erroneous indications of distance. It is a still further object oi.' this invention to provide in a radio echo ranging system a means for changing the maximum calibrated range of the system at will. It is another object of this invention to provide means for altering at will th'e pulse rate of a radio echo ranging system, Other objects will become apparent from a consideration of the following description when taken together with the accompanying drawings in which:

Fig. 1 is a block diagrammatic showing of -a radio echo ranging system;

Fig. 2 is a fragmentary circuit diagram illustrating one embodiment of the invention;

Fig. 3 is a plan view of a. fragment of the viewing screen of a cathode ray tube showing a scale and a. time trace related theretoand bearing deviations indicating the reception of echoes;

Fig. 4 is a view similar to that of Fig. 3 showing the results of shifting th'e pulse frequency of the system in accordance with the invention;

Fig. 5 is a fragmentary circuit diagram illustrating the normal manner of impressing the receiver output upon the deecting plates of the oscillograph;

Fig. 6 is a view similar to that of Fig. 5 showing the manner of incorporating the receiver output inverting mechanism of the invention in the circuit of that iigure;

Fig. 7 is a fragmentary circuit diagram showing means for changing the 'frequency of the control oscillator in synchronism with the inversion of the receiver output;

Fig. 8 is a fragmentary circuit diagram showing means for adjusting the position of the time trace with respect tothe scale on the viewing screen;

Fig. 9 is a plan view of a portion of the viewing screen of the oscillograph showing the eiiect on the echo indications of the practice of one form of the invention;

Fig. 10 is a plan view of a fragment of the system showing three switches mounted on a. single shaft, and

Fig. 1l is a view similar to that of Fig. 9 sh'owing the appearance of the indications on the viewing screen of the oscillograph during one mode of operation.

A known type of echo ranging apparatus is shown in Fig. l. It comprises -a control oscillator I0, the output of winch goes to a pair of buffer amplifiers I I and I2. The oscillator I0 through amplifier II controls the self-keying transmitter I3 which transmits pulses at regular intervals to antenna I4. The oscillator I0 also, through ampliier I 2, controls the sweep generator I 5, the outbut of which is appliedto the deflection plates I1 of cathode ray tube I6 thus producing a recurring time trace on the screen of the tube, which trace is synchronized with the pulse transmission.

A receiver I9 is excited from antenna I4 and has and shown parallel thereto is a time trace 22 extending along one coordinate and bearing various echo indications extending unilaterally of the time trace along a coordinate at right angles to the trace. At the extreme left hand end of the trace is the indication 23 caused by the transmission of the pulses. Scattered along the trace ,are other indicationswhich are caused by echoes from objects in the vicinity, one opposite the 10-milev division of the scale being marked 24 and one marked 25 occurring opposite the 16- mile point of the scale. Others marked 26, 2l and 28 appear opposite the 3-mile, 5-mile and 23-mile points of the -scaie respectively."

Thus from looking at the viewing screen one would assume the presence of objects at distances of 3, '5, 10, 16 and 23 miles from the ranging apparatus. However, any one of these indications' may be erroneous. For example, the 3-mile indication might be a reiiection from an object distant 28 miles and so on. l

By utilizing the invention the character of the indication can be rendered immediately ap-- parent. This may be accomplished by changing the frequency of the pulse transmission or in other words changing the time interval between pulses. Fig. 4 illustrates the results of following this procedure. The time trace as shown in Fig. 4 has been reduced from 25 to 24 miles. This change has of course been accompanied by a reduction in the time interval between pulses so that the time interval is just sufficient to allow energy from a pulse to travel a distance of 24 miles and return. It will be noted in Fig. 4 that all the indications remain the same except those numbered 24 and 25. The indication 24 which formerly appeared at 10 miles now appears at 11. That numbered 25 which formerly appearedV at 16 miles now appears at 19. It is now obvious that the object producing the reflection causing the indication 24 is not distant 10 miles but is distant 35 miles and the object producing the indication 25 is not distant 16 miles but is 91 miles away.

A simple and effective means for achieving this result is illustrated in Fig. 2. This figure shows a portion of the control oscillator I comprising the oscillating tube 29 having a control electrode 30. the frequency of the tube being controlled by a tuned circuit made up of inductance 3I and variable condenser 32. shunted across the condenser 32 is another condenser 33. This condenser may be cut in/ or out of-the circuit at will by means of a switch 34 controlled by a push button 35 from the instrument panel 36 of the device.

A second embodiment of the invention is illustrated in Figs. to 9 inclusive. In utilizing his embodiment the desired results are achieved by inverting the receiver output at regular intervals of time so that indications occur both above and below the time trace. This action is accompanied by synchronized changes in the control oscillator frequency so that each time the output is inverted the frequency simultaneously changes by a predetermined amount. Thus the indications appearing above the line will be v made at one pulse frequency and those below the line 'at4 another. This results in a shift of the llocation of erroneous indications just as was lsecured by use of theiirst embodiment.

In Fig. 5 is shown the final tube 40 of receiver I9, the output of .which isv being applied to one of the deflection plates. In Fig. 6 the output of the receiver has been passed through a rotary switch 46 comprising a shaft 4I and a'1'80v conl 'l tact member 42 secured for rotation with shaft 4I. Thev output of the receiver is applied to the shaft 4I by means of contact 43 riding on shaft* 4I. A pair of resilient contact members 44 and 45- are each connectedl to one of Athe plates I8 and are positioned l180 apart in the pathof the contact member 42. The switch 46 is rotated at 'a-constant speed with the result that the output of the receiver is alternately applied to each of plates I8 at regular intervals.

Fig. '7 shows a means for changing the pulse frequency'in synchronism with the inversion of the receiver output, The control oscillator I0 is shown providedwith a tuned circuit 50 which controls its frequency and also with a condenser 5I adapted to be shunted across this circuit through switch 46'. This is accomplished by con- Atacts 52 and 53. Contact 52 is positioned in the plished by the usual adjusting knob provided for this purpose. However, when the automatic means of the second embodiment is employed such manual adjustment cannot be effected. It can, however, be accomplished by the automatic means shown in Fig. 8. This means employs the switch 46" which simultaneously with each receiver output inversion and oscillator frequency.`

change from normal changes the average bias potential of one of the plates II of the oscillograph. 'I'he direction and amount of this change is controlled by potentiometer 60, which is adjustable at the panel independently of dual potentiometer .62', which, with'out 60, is the usual means for adjusting the centering of the time trace. Potentiometer 60 is shown connected to the right plate II in the figure. The plates I1 are shown connected to tubes 63 and 64 of the sweep generator I5. The potentiometer 60 is so adjusted as to automatically shift the time trace each time the receiver output is inverted, and the switch 46" simultaneously closed, by an amount such that the left hand end of the time trace remains opposite the zero mark of the scale.

Fig. 9 shows the appearance of the indications on the time trace resulting from the employment I of this embodiment of the invention. It should be noted that the indicationsl 23, 26, 21, 28 remain unchanged in position when inverted, the

with the segments of the shaft upon which are mounted semi-cylindrical contact members 42, 42' and 42" respectively.

The automatic frequency changing mechanism of Fig. 7 and the centering mechanism of Fig. 8 may be used without inversion of the receiver output, if desired. By slowing the-speed of the rotating switch the eye can follow the shift of spurious indications. The same result can be accomplished by alternately starting and stopping the shaft 4| bearing the rotary switches 46, 46 and 48" at a speed such that the shift can be seen. Multiple range echoes can also be identiiled without inversion and without slowing down the speed of the rotating switch since they will appear paired, each indication at one half intensity and with its base line filled in, as shown in Fig. 1l. The result in the presence of many echoes would be confusing however.

It will thus be noted that the invention affords a method and means for either manually or automatically determining the true character of the range indications of an echo ranging device. The automatic means affords instantaneous and continuous information as tc the character of the received indications without requiring any attention from the operator.

The invention described-herein may be manufactured and used by or 'for the Government of the United States of America for` governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A radio pulse echo system comprising means for transmitting a regular series of pulses, means for receiving the reflections of said pulses from reflecting objects, a cathode ray tube, means forming on the viewing screen of said tube a recurring time trace synchronized with said pulse transmission. means forming on said time trace indications of the reception of said reections, a scale in juxtaposition to said time trace and having its zero mark opposite the point of origin thereofI means for changing the frequency of said pulse transmission and means for maintaining the point of origin of said time trace opposite the zero mark of said scale, the rate of movement of said time trace remaining constant.

2. A radio pulse echo system comprising means for transmitting a regular series of pulses, means for receiving the reflections of said pulses from reflecting objects. a cathode ray tube, means forming on the viewing screen of said tube a recurring time trace synchronized with said pulse transmission, means forming on said time trace indications of the reception of said reilections, a scale in juxtaposition to said time trace and having its zero mark opposite the high point of origin thereof, and means for changingthe frequency of said pulse transmission, the rate of movement of said time trace remaining constant.

3. A radio pulse echo system comprising means for transmitting a regular series of pulses, means for receiving the reflections of said'pulses from reecting objects, a cathode ray tube, means forming on the viewing screen of said tube a recurring time trace synchronized with said pulse transmission, said time tracehaving its origin located in a predetermined position on `said viewing screen, means formingson said time trace indications of the reception of said reflections, means for changing the frequency of said pulse transmission while maintaining said time trace in synchronism with said transmission and means for maintaining/the origin of said time trace in the same position as before, the rate of movement of said time trace remaining constant.

4. A radio pulse echo system including in combination means for transmitting a regular series of pulses, an indicator, means for receiving said pulses after reflection from wave reflecting objects and for applying said received pulses to produce indications on said indicator, along a locus having its point of origin at a predetermined position on said indicator. the distances of the indications of said received pulses from said point of origin being a measure of the distance of said reflecting objects from said transmission means, and means for varying the interval between transmission of said pulses and simultaneously varying the length of said locus by a proportionate amount, whilermaintaining unchanged the location of the indication of every reection received during the pulse interval immediately following transmission of the pulse which initiated it 5. A radio pulse echo system comprising a control oscillator, a pulse transmitter governed thereby for the transmission of a regular series of radio frequency pulses, a cathode ray tube, a sweep generator governed by said control oscillator and arranged to impress a recurring time trace along one coordinate on the viewing screen of said tube in synchronism with said pulse transmission, a receiver for receiving said transmitted pulses and reflections of said pulses from reiiecting objects, means to impress the output of said receiver upon said tube in a manner to cause said time trace to deviate unilaterally with respect to said time trace along another coordinate upon the reception of one of said pulses or a reflection thereof, means for periodically changing the frequency of said oscillator by a predetermined amount, means to simultaneously invert the output of said receiver applied to said tube and means to simultaneously adjust the position of said time trace to maintain constant the position of its point of origin.

6. A radio pulse echo system comprising a control oscillator, a pulse transmitter governed thereby for the transmission of a. regular series of radio frequency pulses, a cathode ray tube, a sweep generator governed by said control oscillator and arranged to impress a recurring time trace along one coordinate on the viewing screen of said tube in synchronism with said pulse transmission, a receiver for receiving said transmitted pulses and reflections of said pulses from reiiecting objects, means to impress the output 0f said receiver upon said tube in a manner to cause said time trace to deviate unilaterally with respect to said time trace along another coordinate upon the reception of one of said pulses 0r a reiiection thereof, and a common switching means periodically and simultaneously changing the frequency of said control oscillator by a predetermined amount, inverting the output of said receiver applied to said tube, and adjusting the position of said time trace to maintain stationary its point of origin.

' synchronized with said pulse transmission, applying said' received pulses to said time trace to cause deviations therein which act as indications of the distance of the objects reecting said pulses,

' and simultaneously 'changing the rate of said pulse transmission and the length of said time trace by proportionate amounts while maintaining constant the rate of generation of said time trace.

8. In a radio pulse echo system the'method of distinguishing between true and erroneous indications of distance which comprises transmitting pulses at a predetermined rate, receiving said pulses after reection, generating atime trace synchronized with said pulse transmission,

applying said received pulses tosaid time trace to cause deviations therein which act as indica;

tions of the distance of the objects reflecting said pulses, simultaneously changingA the rate of said pulse transmission and the length of said time trace by proportionate amounts while maintains ing constant the rate of generation of said time trace, and maintaining in a fixed position the point of origin of said time trace.

9. In a radio pulse echo system the method of distinguishing between true and erroneous indications of distance which comprises transmittingpulses at a predetermined rate, receiving said pulses after reection, generating a time trace synchronized with said pulse transmission, applying said received pulses to said time trace to cause unilateral deviations therein which act as indications of the vdistance of the objects reflecting said pulses, periodically andI simultaneously changing the rate of said pulse transmission and the length of said time trace in a xed position and maintaining constant the rate of generation of said time trace.

10. In a radio piilse echo system the method of distinguishing between true and erroneous indications of distance which comprises transmitting pulses at a predetermined rate, receiving said pulsesafter reflection, generating a time trace synchronized with said ,pulse transmission, applying said received pulses at said time trace to cause deviations thereiny which act as indications of the distanceof the objects reecting said pulses, periodically and simultaneously changing the rate of said pulse transmission and the length of said time trace by proportionate amounts, while maintaining the point of origin of said time trace in a fixed position and maintaining constant the rate of generation of said time trace.

11. A pulse echo system including in combination means for transmitting distance indicating pulses, a cathode ray indicator, means for receiving said pulses and for applying saidpulses to said indicator to indicate reflected pulses, means for sweeping said ray along a scale to indicate the'distances of the reflecting surfaces, and meansifor maintaining said sweep rate with respect to aunit distance and for changing simultaneously the rate of said pulse transmission and the maximum distance range of said indicator. ROBERT M. PAGE.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Smith Jan. 10, 1939 

